Arctic | Mammals DOCTORATE POSTER PRESENTATION Biomarkers of estrus in wild and zoo-housed polar bears Presenter: Monica Brandhuber , mebrandhuber@alaska.edu, University of Alaska Fairbanks Shannon Atkinson , shannon.atkinson@alaska.edu, University of Alaska Fairbanks Karyn Rode , krode@usgs.gov, US Geological Survey Todd Atwood , tatwood@usgs.gov, US Geological Survey Ryan Wilson , ryan_r_wilson@fws.gov, US Fish and Wildlife Service Erin Curry , erin.curry@cincinnatizoo.org, Cincinnati Zoo and Botanical Garden
Climate change is the largest threat polar bears ( Ursus maritimus ) face due to their dependence on sea ice for hunting and other activities. Nutritional stress resulting from decreased hunting success may negatively impact reproductive rates, so it is important to develop tools to improve reproductive monitoring in wild populations. Previous research in zoos has suggested three biomarkers in feces to detect estrus and potentially predict reproductive success. The goal of the present study was to determine if the same hormone suite could detect estrus in the serum of wild polar bears collected during the spring breeding season using enzyme immunoassay techniques. Testosterone, a reproductive hormone associated with estrus, was significantly higher (p < 0.05) in the serum of wild females in estrus (median = 3.16 ng/g) than wild single females not in estrus (median = 0.49 ng/g), but did not differ by polar bear subpopulation. Cortisol, a major stress hormone, was significantly lower in zoo-housed females (median = 44.24 ng/g) than wild females, with those in the recently-declined Southern Beaufort Sea subpopulation exhibiting significantly lower concentrations (114.83 ng/g) than the stable Chukchi Sea subpopulation (223.65 ng/g). Cortisol did not differ significantly by reproductive status, although wild females in estrus generally exhibited higher concentrations than other reproductive statuses. Dehydroepiandrosterone sulfate (DHEAS), the transit form a poorly-understood hormone that may be related to reproduction or stress mitigation, was significantly higher in wild females in estrus (median = 3.47 ng/g) than wild single females not in estrus (median below assay limit of detection, LOD = 0.0378 ng/g). Serum samples from zoo-housed polar bears, also collected during the spring, exhibited significantly higher DHEAS concentrations (7.46 ng/g) than wild polar bears. DHEAS concentrations did not significantly differ between wild subpopulations. Wild females with cubs exhibited the broadest range in concentrations for all three hormones, with median concentrations that did not significantly differ from other reproductive statuses. These findings suggest that monitoring serum hormone concentrations may provide valuable insight into reproductive activity and environmental stress levels for both wildlife and zoo managers.
Alaska Marine Science Symposium 2023 271
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